Lying among the tools, ballast and spare parts littering the floor of the Hunley, the rectangular copper plate looked like something from a UFO.

Drilled with holes, lined with symmetrical ridges and laced with traces of zinc, the plate at first raised more questions than it answered about the Confederate submarine.

But put it together with strange coils of wire and other things found onboard, and the plate suggests the crew might have used a battery-powered torpedo to sink the Housatonic.

"It's the kind of thing if I were trying to build a battery in the 1860s that I would have used," Mike Drews, a material science professor at Clemson University, said. "Having a piece of copper sheeting by itself isn't that strange, but this piece doesn't look like what you'd expect."

Clemson is expected to begin an analysis of the plate next week to see what else scientists can learn. The clues that Hunley scientists have gathered so far hint that the sub was experimenting with battery technology.For starters, the artifact looks similar to the copper and zinc plates used to build batteries in those days. It was found in the captain's compartment, where commander George Dixon was in charge of the torpedo. It was within an arm's reach of a coil of wire and also a twisted wire with a noose on the end that could have served as a trigger. There doesn't appear to be wire used on any other part of the sub.

While all this evidence is circumstantial, it is promising nonetheless. It means that the Hunley may have been not only the first sub to sink an enemy ship, but the first ship of any kind to sink a ship using battery-powered weapons.

"It is not enough to say there was an electrical system on the Hunley, but we cannot rule it out," said Paul Mardikian, the sub's senior conservator.

Although the Hunley's predecessor, the American Diver, was briefly fitted with an electro-magnetic engine, there is little chance a battery -- if onboard -- had any other use than weaponry. And, by the time the Hunley was launched, electrically detonated mines were the cutting edge of wartime technology.

Confederates allegedly sank the USS Cairo with the first electric mine, which was attached by wire to the shore. The Union Navy's submarine, the Alligator, was meant to take divers underwater to plant electrically detonated charges beneath enemy ships, but it was lost before it ever saw action. In August 1864 -- more than six months after the Hunley sank the Housatonic off Sullivan's Island on Feb. 17 of that year -- Confederates used electric torpedoes to sink a Union ship in the James River.

The technology took off after the war. In the late 1860s, the British Navy began experimenting with electric torpedoes, but did not perfect the system until the 1870s.

Until now, most scientists have speculated the Hunley's spar-mounted torpedo was triggered by a rope lanyard that through friction or some other means detonated the 90-pound charge of gunpowder in the torpedo. That still may be the case. It could be that the sub was merely experimenting with battery detonators, or used both methods. Hunley research has shown, time and again, that the crew was prepared for Plan B.

"We had two pumps and deadlights reinforcing the glass ports along the top of the submarine," said Sen. Glenn McConnell, chairman of the Hunley Commission. "If the torpedo could also have been electrically detonated, this would be right in line with the Hunley to have fail-safe measures in place for all her critical functions. This would be a cutting-edge upgrade to an already state-of-the-art firing system."

Another, yet related, explanation for the wire onboard the sub also concerns the spar, the pole attached to the front of the sub. The lanyard used to trigger the spar may have been wire instead of rope. Wire would have been more hydrodynamic, less likely to tangle, and nearly invisible.

And the spool mounted on the sub, as depicted in contemporary art, was not nearly big enough to hold hundreds of feet of rope. But it could have handled that much wire easily.

That, however, does not explain why the crew would have had a battery onboard.

The absence of other material is pretty easy to explain. Drews said zinc plates would have disintegrated -- that was their job in a battery -- and the paper or cloth separating the plates could have rotted, as well. If traces of such things remain, Clemson scientists should find them in their study.